Cabs of construction equipment have been structured in the form of nearly like rectangular boxes by joining steel members together by welding. For example, a representative example of a cab of a hydraulic excavator which is a typical construction equipment is realized in the shape of a box by, first, sub-assembling various portions for forming the cab, erecting the right and left sub-assembled side panels, and joining rear and roof panels between them (e.g., see patent document 1).
When it is required to impart strength to the cab to cope with such cases as when the equipment might turned over or when a material might fall down thereon, steel pipe pillars are stud in the cab, and the side, rear and roof panels are joined to the pillars to complete the cab (e.g., see patent document 2).                Patent document 1: JP-A-2001-140283 (FIG. 5)        Patent document 2: JP-A-2005-335474 (FIG. 7)        